1. Field of the Invention
This invention relates to dye-sensitized solar cells. In particular, it relates to dye-sensitized solar cells having a light-permeable tube-shaped vessel.
2. Description of Related Art
Heretofore, development of solar cells as new energy sources with less influence on the global environment has been performed. Solar cells utilizing silicon semiconductors have a high conversion rate and an excellent light stability and therefore are generally widely used. However, from the viewpoint of manufacture, there are the problems that conditions of a high temperature and a high vacuum are necessary, so that it is difficult to implement large area cells, and the production costs are high.
Dye-sensitized solar cells wherein an electrolytic solution is filled into the interior of a transparent vessel, a photoelectrode of a porous semiconductor to which a dye has been adsorbed, and a counter electrode are provided, and electric energy can be output by utilizing the fact that the dye being irradiated with sunlight emits electrons are known (see, Japanese patent laid-open publication 2007-12545). This kind of solar cell has the advantage that no high vacuum chamber is necessary for the production, so that the burdens with regard to the facilities are reduced, and a low-price production becomes possible.
FIG. 5(a) is a cross-sectional view along the direction of the tube axis of the conventional dye-sensitized solar cell shown in the Japanese patent laid-open publication 2007-12545, and FIG. 5(b) is a cross-sectional view along line Z-Z′ in FIG. 5(a).
As to this solar cell 8, a transparent conductive layer 82, a dye-sensitized porous semiconductor layer 83 to which a dye has been adsorbed, and an electrolyte layer 84 are provided successively on the inner surface of a tube 81 made from a transparent material, and a counter electrode 85 is inserted into the interior of the tube 81 along the longitudinal tube axis. One end part 85b of the counter electrode projects outward from the tube 81. The space between an end part 81b of the tube 81 and the end part 85b of the counter electrode 85 as well as the space between the other end part 81a of the tube 81 and the other end part 85b of the counter electrode 85 are insulated and sealed by means of a sealing member 86 made, for example, from epoxy resin, thus the electrolytic solution of the electrolyte layer 84 does not leak out to the outside of the tube 81. The lead wires 87, 88 are connected to the counter electrode 85 and the transparent conductive layer 82 respectively.
When this solar cell 8 is irradiated with sunlight, the sunlight passes through the tube 81 and the transparent conductive layer 82 and reaches the dye-sensitized porous semiconductor layer 83, a photochemical reaction occurs and electrons are emitted by the dye, by means of which an electromotive force is generated between the lead wires 87, 88.
Because, by means of this configuration, the vessel has a cylindrical shape, the change in the electric power generation with regard to the incident angle of the light can be significantly reduced.